"The most important finding in this study is the high survival of extremely preterm infants born alive," say Dr Mats Blennow and colleagues of Karolinska University Hospital in Huddinge, Sweden.

In a study of more than 1,000 preterm babies, 707 were born alive and 304 stillborn between 2004 and 2007, they say.

The overall perinatal mortality ranged from 93% at 22 gestational weeks to 24% at 26 weeks, say Blennow and colleagues.

They found of the babies delivered alive, 70% lived beyond the year long study, with the rest dying in the first week or in the delivery room.

Infants who survived 28 days were all equally likely to survive, regardless of how premature they were.

Premature births increasing

In recent decades more babies are being born pre-term, in part because fertility treatments lead to multiple pregnancies, which in turn are more likely to cause early labour.

But, the researchers say, doctors may assume these very early 'premmies' are not going to live, and may not offer treatments that could give them a fighting chance.

The study found that if doctors used tocolytics, drugs that delay delivery, or corticosteroids and surfactants to prevent the lungs from filling with water, babies were far more likely to live.

"Therefore, non-initiation or withdrawal of intensive care for extremely preterm infants cannot be based solely on a notion of unlikely survival," the researchers say.

But Blennow and colleagues say this does not suggest all extremely preterm infants should be kept alive at any cost.

"The prognosis, based on an individual assessment, including early and subsequent morbidities, and parental desires are still the most important factors in decision-making," they say.

The bigger picture

Molecular endocrinologist Richard Nicholson, of the John Hunter Hospital in Newcastle, says this research confirms that improvements in neonatal care greatly increase the survival rate of pre-term babies.

But Nicholson says premature babies not only have an increased risk of death soon after birth but also suffer other diseases, such as cerebral palsy, that remain with them for life.

"The biggest problem they don't point out in the paper is that we need a greater understanding of what causes preterm birth," he says.

Nicholson says the causes of premature birth are largely unknown and between 6-10% of Australian babies are delivered prematurely.